1. Field of the Invention
The present invention relates to an encoder system as a control system which includes an actuator such as an AC servo motor, for example, used in industrial robots, a position sensor such as an encoder for detecting the positional displacement of the actuator, and a controller.
2. Description of Related Art
Conventionally, in an encoder system, an encoder was generally disposed on an input shaft side of a motor, and it was necessary to use a multiple-rotation absolute encoder having an external battery in order to obtain multiple-rotation information (namely, multiple-rotation data) which represents the number of rotations of a shaft of the motor. As an example of such conventional art, Japanese Patent Application, Publication No. H04-025388 A is known.
Moreover, as an example of an encoder system (encoder device) of the conventional art, there is known an encoder system in which a planetary reduction gear, for example, is disposed on an output shaft of a servo motor having an encoder mounted thereon, and a servo driver controls the servo motor based on a rotation command signal. There is also known a technique in which, when the planetary reduction gear has a transmission angle error, a rotation angle error of the planetary reduction gear and the input rotation command signal are corrected using an input synchronization correction circuit (for example, see Japanese Patent Application, Publication No. H09-311725 A).